His distinguished scientific career spanned more than 30 years. His research focused on the molecular basis of fertilization, and his studies of germ cells — egg and sperm — have led to key insights into reproductive biology, as well as opened possible avenues toward new contraceptives and ways to increase fertility.

"David was an individual that led by example," said Dr. David Mangelsdorf, chairman of pharmacology at UT Southwestern. "For a scientist of his stature, he was also unpretentious and easy-going, and that made him one of the most sought-after mentors for junior and senior faculty in our department. He was a main reason many of us came to UT Southwestern. We will miss him."

Dr. Garbers was born in 1944 in La Crosse, Wis., where he grew up on a farm. A childhood interest in science eventually led him to the University of Wisconsin-Madison, where he earned a Bachelor of Science in animal science in 1966, a master's in reproductive biology in 1970, and a doctorate in biochemistry in 1972. He completed a postdoctoral research fellowship in physiology at Vanderbilt University School of Medicine in Nashville.

In 1974 he began his career as an assistant professor of physiology at Vanderbilt and became a full professor there in 1982. In 1976 Dr. Garbers was appointed as an investigator of the Howard Hughes Medical Institute (HHMI), a position he continued to hold while at UT Southwestern. He was one of the longest-serving researchers with HHMI, a philanthropic organization that promotes biomedical research and funds about 300 investigators across the country.

He joined the UT Southwestern faculty in 1990 as a professor of pharmacology and in 1999 was named director of the Green Center and holder of the Cecil H. and Ida Green Distinguished Chair in Reproductive Biology Sciences.

"David Garbers had unique strengths and a great work ethic, much of which I'm sure came from growing up on a farm," said Dr. Alfred Gilman, executive vice president for academic affairs, provost and dean of UT Southwestern Medical School.

During his early career at Vanderbilt, Dr. Garbers discovered receptors on the sperm cells of sea urchins that detect signals from the egg, enabling sperm to know in which direction to swim. He and his colleagues later found the same receptors in mammals, where they also are known to be involved in regulating blood pressure, vision and intestinal secretions.

"David was the quintessential biologist and an extraordinary biochemist. He had an enormous instinct for biology and would follow the trail wherever it led him, from sea urchins to mice, from reproduction to hypertension," said Dr. Gilman, who was chairman of pharmacology at UT Southwestern for much of Dr. Garbers's tenure in that department.

Dr. Garbers identified many proteins found exclusively on sperm, including one called CatSper that gives sperm the wiggle necessary to propel them through the egg's membrane. These findings have potential applications in the development of novel forms of male birth control.

Most recently Dr. Garbers devised methods to keep male rat germline stem cells — sperm precursor cells — from differentiating, or changing, into sperm proper. Those studies have brought researchers closer to coaxing such cells to behave like embryonic stem cells, capable of growing into many other types of cells in the body.

He also was developing methods for maintaining and growing male germline stem cells in the laboratory and genetically manipulating those cells. Although genetic modification of human sperm was not one of his immediate goals, his research may one day make it possible to correct genetic defects in humans — cystic fibrosis, for example — by identifying and eliminating in culture a man's sperm stem cells that carry the gene.

Dr. Garbers was elected to the American Academy of Arts and Sciences in 1992 and to the prestigious National Academy of Sciences in 1993. He also was a member of the Academy of Medicine, Engineering and Science of Texas.

He is survived by his parents, Mr. and Mrs. Wilfred Garbers of West Salem, Wis.; a daughter, Lesley FitzGerald of McKinney, Texas; a son, Michael Garbers of Lewisville, Texas; two grandchildren, Hailey and Austin; two sisters, Betty Rhyner of Madison, Wis., and Jeanette Knutson of Poynette, Wis.; and two brothers, Donald Garbers of La Crosse and Randy Garbers of West Salem.

In lieu of flowers gifts may be directed to David L. Garbers Medical Research Fund at UT Southwestern, PO Box 910888, Dallas, TX 75391-0888.